Conventional, in a Long Term Evolution (LTE) network, during handover (HO), a terminal device, for example, user equipment (UE) may perform random access to a target cell managed by a network device (for example, an eNB) to gain synchronization with the target cell. More specifically, the terminal device may initiate the random access channel (RACH) process and transmit a physical random access channel (PRACH) preamble for initial network access. The terminal device may also initiate the RACH and transmit a PRACH preamble signature when the UE is not uplink synchronized but need to send new uplink data or control information. In response to a successful PRACH preamble attempt, the network device may transmit a random access response (RAR) carrying an initial uplink bandwidth assignment to the terminal device.
However, a problem of the conventional solution is that sending one random access preamble during HO may not always work. For example, during beam sweeping, if the network device receives signals via a beam different from the beam used by the terminal device for transmitting the random access preamble, it is highly possible that the network device cannot properly receive the random access preamble. Thus, there is a need to adjust the times of the transmission of the random access preamble to improve the success rate of the random access procedure.